1. Field of the Invention
The present invention relates to a printer having a fixer that adheres a transferred toner image to paper. More particularly, the present invention relates to a method and apparatus for controlling a fixing condition of a printer according to the size and type of paper used in order to improve the print quality.
2. Description of the Related Art
Printers are the most common output devices for printing the results of data processed onto paper in order to check, store, and deliver data from a computer, camera, facsimile and the like. Printers comprise the basic element of multi-functional printers, facsimiles, electronic cash registers, automatic teller machines, and so on.
Various types of printers have been developed such as daisy wheel, dot pin, ink jet, laser printers and especially the ink jet and laser printers, which are widely adopted.
The laser printer uses physical elements such as toner, light (laser or light emitting diode (LED) array), static electricity, heat, and pressure to perform a printing operation. The core technology of the laser printer uses static electricity.
FIG. 1 is a schematic view illustrating a conventional laser printer.
Referring to FIG. 1, a laser printer includes a print unit 100 for printing an image onto paper, a sheet output passage 310, a sheet turn passage 320, a pick-up roller 201, and a feed roller 210.
The print unit 100 includes a charger 120, a Laser Scan Unit (LSU) 130, a photoconductive drum 110, a development unit 140 holding a developer, a transfer belt 150, and a fixer 170. The print unit 100 prints an image on paper, using an electrophotographic method. The development unit 140 of the print unit 100 includes four cartridges respectively holding black (K), cyan (C), magenta (M), and yellow (Y) developers, in order to print a color image.
Operations of forming an image by the print unit 100 are as followings. In a charge operation mode, the charger 120 charges the photoconductive drum 110 uniformly. In an exposure operation mode, the LSU 130 supplies the photoconductive drum 110 with a light corresponding to a color of image data such as a yellow color. The light causes a voltage difference between light exposed and non-exposed surfaces of the photoconductive drum 110, thereby creating an electrostatic latent image of yellow. In a development operation mode, the development unit 140 applies the developer to the electrostatic latent image in order to form a yellow toner image. The developed yellow toner image is transferred to the transfer belt 150.
After the yellow toner image is completely transferred to the transfer belt 150, magenta M, cyan C, and black K toner images are sequentially transferred and overlapped onto the transfer belt 150 with the same method as is mentioned above in order to make a color toner image on the transfer belt 150. The color toner image is transferred onto paper that passes between the transfer belt 150 and a transfer roller 160, and the fixer 170 applies heat and pressure to the color toner image to adhere the image onto the paper, thereby completing a color image print. Herein, the fixer 170 includes a heat roller 171 and a pressure roller 172.
Though the exemplary print unit 100 shown in FIG. 1 is a multi-path type printer that uses one photoconductive drum and one LSU, there are various types of electrophotographic print units that can employ aspects of the present invention.
The sheet output passage 310 connects an outlet of the print unit 100 and a sheet output tray 230. Typically, the fixer 170 is placed at the outlet side of the print unit 100. A pair of rollers 220 is used to eject the paper that has been printed.
When printing an image onto each side of paper, an image is printed on one side of the paper and the paper turns over and returns to the print unit 100 through the sheet turn passage 320. The sheet turn passage 320 is separated from the sheet output passage 310 and extended to the feed roller 210.
FIG. 2 is a block diagram illustrating a conventional circuit construction of a printer.
Referring to FIG. 2, the printer 200 includes an interface 202, a controller 204, a memory 206, a lookup table 208, an input/output (I/O) interface 210, an operator panel 212, and a print engine 214.
The operator panel 212 includes a plurality of keys for receiving various commands from the user and a display for presenting operational information to the user.
Through the interface 202, command signals, print data, and the like are received from the host computer (not shown) and signals such as printing status signals are sent to the host computer. The received print data from the host computer is buffered in the memory 206.
The controller 204 communicates with the host computer through the interface 202 and controls the print engine 214 to print the print data according to commands from the host computer and the operator panel 212. The controller 204 can also access lookup tables from lookup table 208.
The memory 206 stores setup values from the operator panel 212 and print data from the host computer under the control of the controller 204. Also, the memory 206 may store an operating program of the controller 204.
The I/O interface 210 connects the controller 204, the operator panel 212, and the print engine 214, for exchanging data such as input/out signals of the controller 204. The print data is transmitted to the print engine 214 through the I/O interface 210.
The print engine 214 includes many devices for feeding paper and printing on the paper, and performs the printing operation under the control of the controller 204.
Since the laser printer uses heat to affix the toner onto the paper, operational properties of the fixer 170 must be properly adjusted according to the size and type of the paper to be printed. For example, the fixing temperature and fixing speed must be properly set according to the size and type of the paper in order to affix the toner onto the paper thoroughly.
For this, the size and type of the paper are selected through a printer driver of the host computer in the related art.
FIG. 3 is a table illustrating the relationship between paper properties and fixing conditions of a printer shown in FIG. 2. T and V denote a reference temperature and a reference speed for fixing, respectively. ΔT1-ΔT4 and ΔV1-ΔV4 differ with respect to the type of paper used. T, V, ΔT and ΔV vary depending on the manufacturer and the model used. However, in general, the fixing temperature and fixing speed for thick paper and OHP are inferior to those for other types and sizes of paper.
The lookup table 208 stores a table shown in FIG. 3 and the controller 204 uses the values in the table 208. The controller 204 controls the fixing operation of the print engine 214 with the paper information of the printer driver and the fixing conditions of the lookup table 208.
FIG. 4 is a flow chart illustrating a method of controlling a conventional fixer.
Referring to FIG. 4, when a printing operation starts, the size and type of the paper are selected using the printer driver in step S402.
In step S404, the controller 204 sets the fixing speed and temperature of the print engine 214 according to the size and type of the paper selected from the printer driver.
In step S406, the development unit 140 of the print engine 214 forms a toner image on the photoconductive drum 110 and the transfer belt 150.
In step S408, the image transferred onto the transfer belt 150 is transferred to the paper.
In step S410, the fixer 170 of the print engine 214 performs a fixing operation according to the fixing speed and temperature set in step S404.
After above operations, the paper is output and the printing operation ends.
As described above, in the related art method of controlling the fixer of the printer, the fixing conditions (temperature and speed) is set before starting a printing operation according to the paper conditions (size and type) selected using the printer driver, and the printer performs the fixing operation according to the fixing conditions. However, if the paper conditions selected using the printer driver is not correct, the fixing operation is performed improperly.
The drawback of the related art method is that there is no way of correcting the paper conditions during printing operation when the selected paper conditions and actual paper conditions are different.
Accordingly, there is a need for setting fixing parameters based on actual paper size rather than a predetermined paper size.